Heretofore, there has been known a construction machine provided with a base frame which supports a working attachment so as to be raised and lowered and also provided with an engine installed on the base frame.
In construction machines of this type it has recently been desired that an exhaust gas after-treatment device for purifying exhaust gas from an engine be installed on a base frame.
More particularly, the aforesaid exhaust gas after-treatment device has a DPF (Diesel Particulate Filter) for decreasing the amount of dust such as soot and mist contained in the engine exhaust gas and also has a reduction catalyst for decreasing the amount of NOx contained in the exhaust gas (see, for example, Patent Documents 1 and 2).
However, since the engine and related peripheral devices (e.g., hydraulic systems) are disposed in a planarly massed layout on the base frame, it is difficult to newly ensure on the base frame a space as a planar space for disposing the exhaust gas after-treatment device, and if a new space is ensured above the base frame, the construction machine itself becomes larger in height.    [Patent Document 1] Japanese Patent Laid-Open Publication No. 2003-90214    [Patent Document 2] Japanese Patent Laid-Open Publication No. 2003-120277